Indoor and outdoor display devices such as billboards are well known in the art. While such displays provide maximum message area for total sign area, billboards are limited in that only a single message may be conveyed unless the entire billboard is redone.
Another prior art display is shown in Ray U.S. Pat. No. 1,461,047 or Reed U.S. Pat. No. 3,199,239 and comprises a plurality of triangular elements rotatably disposed adjacent one another. The elements turn simultaneously to provide three displays, each similar to a simple billboard. While this type of display provided triple message capability, only limited flexibility is provided since each of only three messages can be displayed without refinishing the sign.
A different display system is suggested by Charles U.S. Pat. No. 874,832, in which a plurality of triangular elements are disposed in rows and columns to form a matrix, each column of elements being affixed to a spindle for rotation. However, the device is limited in that entire columns of elements, rather than individual elements, are rotated, and therefore only three messages can be displayed. Aoyama U.S. Pat. No. 3,307,170 shows a similar display which includes an electromechanical means for rotating each triangular element individually, to permit the user to selectively rotate groups of elements to display a desired message.
While the display of Aoyama U.S. Pat. No. 3,307,170 provided increased flexibility by permitting the user to selected and vary the message displayed, the electromechanical clutching and rotation devices associated with, but external to, each element for selecting the proper viewing face are of such complexity and size that repairs are difficult to make, and the structure cannot readily be incorporated in an element of small dimension. In addition, such electromechancial devices require considerable energy for operation, and the use of solenoids occasionally resulted in incomplete rotation of the elements, yielding poor resolution.
The electromechanical structure shown by Aoyama was improved upon in an invention disclosed in patent application Ser. No. 581,943, filed May 29, 1975, and assigned to F&M Systems Company, which application disclosed simplified clutching and drive mechanisms. However, even such improved systems are of such complexity that repairs can be difficult. Also, since a single rotating spindle extends through each column of elements, replacement of a single element involved substantial disassembly of the sign.
A different approach is shown in Lacy U.S. Pat. No. 3,924,226, also assigned to F&M Systems Company. Lacy discloses a display comprising a matrix of electromagnetically positioned elements, each element being housed in a liquid-filled chamber and caused to rotate by the attraction between an energized electromagnet located outside the housing and a permanent magnet or magnets located within the element itself. While this approach eliminated the need for axles, shafts, bearings, and other mounting and rotation means, use of a located-filled housing presented maintenance problems. The lack of a mounting assembly coupled to the the element resulted in poor detenting; and when the elements were arranged in a matrix display, magnetic interaction between the elements resulted in poor resolution.
Displays using incandescent lighting have found favor for such uses as time, temperature and message displays. However, such displays consume considerable amounts of energy. Further, the visibility of incandescent displays is substantially reduced in bright sunlight.
An electromagnetically actuated display element employing stators has been found to satisfactorily operate in systems using only a few elements such as meter readouts and the like. One such device is shown in Morreale U.S. Pat. No. 3,253,127, where a housing is affixed to a ring magnet and the combination thereof rotates around a five-poled stator. Application of positive and negative pulses to five coils permits a ten position digital readout. Also see Silverman U.S. Pat. No. 3,479,626, which discloses a rotary two-poled magnetic drum disposed around a twelve-poled stator. The drum is indexed by interaction of pulses applied to one or more of the stator coils, each of which is wound across a plurality of stator lobes, to display a message located on a housing attached to the magnet.
Other devices have employed configurations wherein a plurality of stationary stator coils surround a rotatable magnetic core, with the housing or other indicator affixed to the rotatable core. See, for example, Kulka U.S. Pat. No. 3,766,549, Lang U.S. Pat. No. 3,353,174 (note FIG. 3), and Watkins Pat. No. 3,412,615. Such display elements are complex and expensive to manufacture, as well as being suitable only for small displays viewed from a short distance. Such devices are not suitable for a matrix type display since the elements are of such shape and size that a matrix display would yield a very poor ratio of message area to total sign area.
It is therefore one object of this invention to provide an improved display element.
It is another object of this device to provide an improved display element suitable for use in a matrix arrangement.
It is a further object of the present invention to provide a display element which requires power only during changes in the displayed message.
It is another object of this invention to provide an improved multi-faceted display element wherein the elements for selecting the proper viewing face are substantially incorporated within the display element.
It is another object to provide a display element requiring minimal maintenance.
It is another object of the present invention to provide a substantially maintenance-free display for interior and exterior use.
It is a further object of the present invention to provide a display which does not require continuous power.
It is another object of the present invention to provide a display which provides a good proportion of message area to total sign area.
It is another object of the present invention to provide a display element which may be reliably mass produced at low cost.
It is a further object of this invention to provide a display which is readable under ambient daytime lighting.
It is a further object of this invention to provide a display which operates on low voltages.
It is a further object of the present invention to provide a display with low power consumption.
It is a further object of the present invention to provide a display element having readily disconnected contacts which are substantially weatherproof when connected.
Other and further objects of the present invention will be apparent in the course of the detailed description of the invention which follows.